Feds to Investigate BP Managers Two men who were on the rig when it exploded targeted By Kevin Spak, Newser Staff Posted Jul 23, 2010 5:11 AM CDT 5 comments Comments The Deepwater Horizon rig is seen burning in this April 21, 2010 aerial photo. (AP Photo/Gerald Herbert) (Newser) – Federal investigators have named two BP managers as “parties of interest” in their probe of the Deepwater Horizon explosion. Both men were aboard the rig when it blew, the Wall Street Journal reports. One, Robert Kaluza, BP’s employee overseeing rig operations, has twice been called to testify in the investigation, and declined by citing his Fifth Amendment rights. The other man is BP’s vice president of drilling, Patrick O’Bryan. Five Transocean employees have previously been named as parties of interest as well, along with BP and Transocean in general. Internal investigation documents have also revealed a potential cause of the Blowout Preventer failure: A switch aboard the rig known as the “deadman switch,” which should have triggered the preventer, had been rebuilt by an “unknown person” and was inoperable when workers tried to activate it.